System, garment and method

ABSTRACT

The present invention relates to a system and garment that incorporates sensors that can be used for measuring or monitoring pressure or forces in feet, the stumps of limbs of an amputee that are fitted with prosthetic devices, or any other parts of the body that are subject to forces such as the buttock while seated or when external pressure inducing devices are employed, such as for example, pressure bandages. The invention also relates to a method to monitor or diagnose any foot or limb related activity for recreational, sporting, military or medical reasons and is particularly aimed at the treatment of neuropathic or other degenerating conditions.

This application is a filing under 35 U.S.C. §371 of InternationalPatent Application PCT/AU2008/001245, filed Aug. 22, 2008, which claimspriority to Australian Application No. 2007904520, filed Aug. 22, 2007,the entirety of each is hereby incorporated herein by reference.

FIELD AND BACKGROUND OF THE PRESENT INVENTION

The present invention relates to a system and garment that incorporatessensors that can be used for measuring or monitoring pressure or forcesin feet, the stumps of limbs of an amputee that are fitted withprosthetic devices, or any other parts of the body that are subject toforces such as the buttock while seated or when external pressureinducing devices are employed, for example, pressure bandages. Theinvention may also incorporate other sensors for monitoring physicalconditions such as temperature, strain, stress or angulation or sensorsfor monitoring physiological conditions such as the make up of sweat orbody exudate. Moreover, the invention also relates to a method tomonitor or diagnose any foot or limb related activity for recreational,sporting, military or medical reasons and is particularly aimed at thetreatment of neuropathic or other degenerating conditions.

Diabetes, alcoholism, uremia, AIDs, or nutritional deficiencies areconditions that are well known as causing damage to nerve endings knownas peripheral neuropathy. Other less common causes include exposure tocold or radiation, physical injuries, a few medicines, toxic substances,vascular or collagen disorders, systemic lupus erythematosus,scleroderma and rheumatoid arthritis. Symptoms of peripheral neuropathyare usually in the form of pain, numbness, tingling, burning or a lossof feeling. The symptoms may also include a sensation that you arewearing an invisible glove or sock; a burning or freezing pain; sharp,jabbing or electric pain; and an extreme sensitivity to touch.

Diabetes also affects the circulation. Poor circulation can affect theability of the body to heal when damage occurs. Healing can take a whileand it is imperative that pressure is removed from the area and goodwound dressings are used, infections can spread, the ultimate of thisprocess is an amputation. Neuropathy is the commonest complication ofdiabetes and usually arises within 5 years of the onset of the disease.Fifty percent of patients with neuropathic joints require some degree ofamputation within 5 years.

Patients with peripheral neuropathy demonstrate a significant increasein loading time, mainly at the heel and at the metatarsal area of thefoot, and they demonstrate a reduction at the hallux: i.e. they becomeflat footed and acquire a hip-based walking strategy.

It has been established from discussions with leading world podiatristsand clinicians that a means for obtaining early diagnosis oridentification of at risk patients would be of enormous advantageenabling early intervention to assist patients with long term solutions.What is required is a device that can provide a measured record of dailyactivity at the foot.

One attempt to address this problem is the Pedar system which ispressure mapping system developed by Novel, Munich Germany. The systemmonitors local loading of the foot inside the shoe and is used for:

-   -   gait analysis    -   rehabilitation assessment    -   shoe research and design    -   aiding in shoe prescription and orthotic design    -   field testing of sport applications    -   kinetic analysis of free gait

However, the system is not suitable for elderly or frail persons orextended wearing by persons with venous illnesses such as diabetes. Theother serious limitation is that these devices are shoe inserts and aretherefore only effective when the person is wearing shoes. It is howeverdesirable to gather information for all walking behaviour with andwithout shoes.

Another attempt is described in German patent DE10314211 which relatesto a sock that has a grid of conducting yarns that provide pressuremeasuring at points of intersection when a person is walking. Thepressure-sensitive material extends over the entire foot region andprovides an insight on the distribution of loads but does not measurepressure or loads in absolute terms nor does it measure other factorssuch as temperature and strain.

SUMMARY OF THE INVENTION

According to one embodiment of the present invention there is provided asystem that is worn by a user to monitor or sense pressure eitherseparately or in combination with any one or more of temperature,stress, strain, angulation or a physiological condition such as the makeup of sweat or body exudate, the system including:

a) one or more than one discrete pressure sensor that can be fitted to,or worn against surfaces subjected to forces or pressure that include,but are by no means limited to, feet or stumps of a limb of an amputee;and

b) electrical circuitry that receives signals from the sensors;

whereby, when in use, each sensor is able to be positioned at desiredlocations on the surfaces subject to forces or pressure of a user tomonitor or sense pressure at the location of the sensors.

Throughout this specification, references to surfaces of a user subjectto a forces include side surfaces such as the ankle or upper parts ofthe foot, and is not limited to parts of the body that are necessarilyrequired to carry the load of the person such as the sole of a person'sfoot while walking or the buttock of the person while seated.

In addition, the words “pressure” and “forces” are used synonymouslythroughout this specification.

One of the advantages of the present invention is that the sensors maybe strategically located to sense and monitor changes to a foot or limbcondition throughout daily activity. In the instance when the inventionis being used to monitor the pressure or forces on a person's foot, aclinician can position the sensors based on their understanding of thewalking characteristics of the user to obtain the most relevant datafrom the sensors. In other words, the invention allows a level ofcustomization to be achieved for individual users.

Preferably, the sensors are movable and can be selectively moved arounddifferent locations to monitor different parts of the user.

Preferably, the system includes a substrate that can be worn by, orfitted directly or indirectly to the surfaces of the user beingmonitored, and said sensors are fixed or moveably connected to thesubstrate.

According to another embodiment of the present invention there isprovided a system that is worn by a user to monitor or sense pressureeither separately or in combination with any one or more of temperature,stress, strain, angulation or a physiological condition such as the makeup of sweat or exudate of the user, the system including:

a) a flexible substrate that can be worn by, or fitted directly orindirectly to surfaces of a user subject to pressure or forces such as,but by no means limited to feet, or stumps of a limb of an amputee; and

b) one or more than one discrete pressure sensor fixed or movablyconnected to the substrate,

wherein the substrate and sensors can be worn directly or indirectlyagainst surfaces of the user and the sensors can be positioned atdesired locations without causing an increase in pressure in the loadbearing surfaces as result of the presence of the pressure sensors.

One of the advantages of the present invention is that use of thesensors do not have any physical effect that could in any way causeadverse effects to the foot or limb at points of contact.

Preferably, the system includes circuitry that receives signals from thesensors.

According to another embodiment of the present invention there isprovided a garment that is worn by a person to monitor or sense pressureeither separately or in combination with any one or more of temperature,stress, strain, angulation or a physiological condition such as the makeup of sweat or body exudate, the garment including:

a) a flexible substrate that can be worn by, or fitted directly orindirectly to surfaces of a user subject to loads or pressure such as,but by no means limited to feet, or stumps of a limb of an amputee; and

b) one or more than one pressure sensor fixed or movably connected tothe substrate,

whereby, when the substrate is fitted or worn to the user, each pressuresensor is able to be positioned at desired locations on the surfaces ofthe user.

The position of the sensors is able to be adjusted by adjusting theposition of the substrate on the user or, in the situation where thesensors are removeable, the position of individual sensors on thesubstrate may also be moved.

According to yet another embodiment of the present invention there isprovided a garment that is worn by a person to monitor or sense pressureeither separately or in combination with any one or more of temperature,stress, strain, angulation or a physiological condition such as the makeup of sweat or body exudate, the garment including:

a) a flexible substrate that can be worn by, or fitted directly orindirectly to surfaces of a user subject to loads or pressure such as,but by no means limited to feet, or stumps of a limb of an amputee; and

b) one or more than one pressure sensor fixed to removably connected tothe substrate,

wherein the substrate and pressure sensors can be worn directly orindirectly against surfaces of the user and the sensors can bepositioned at desired locations without causing an increase in pressurein the surfaces of the sensors.

According to another embodiment of the present invention there is alsoprovided a method of monitoring or treating a patient, the methodincluding the steps of:

placing a pressure sensitive garment, sleeve or bandages in contact withthe buttock, hand, foot or limb of a patient; and

monitoring the pressure readings attributable to either the weight ofthe patient or the pressure applied externally to the patient, forexample, the pressure gradient applied by pressure bandages to a limb ofa patient.

The step of monitoring may involve analysing the signals of pressuresensors located on any one or more part of the patients foot such as theball, heel or toes of a patient including big toe, 1^(st), 3^(rd) and5^(th) metatarsal.

The method may also include the patient performing different movementssuch as walking, running, jumping, stopping and moving from a stationaryposition.

The method of the present invention may also include any one or acombination of the features of the pressure sensitive garment, sleeve,bandages or system as described herein.

DETAILED DESCRIPTION

A series of preferred features that may apply equally to both thesystem, garment and method embodiments of the invention will now bedescribed.

The ability of the sensor to not cause an increase in pressure at thesurface of a user subject to loads or pressure may be achieved by anumber of ways. For example, the substrate may contain recesses thathouse the sensors so as to provide a continuous smooth outer surface andthe housing and sensors have substantially the same hardness orcompression characteristics so as to maintain a relative smooth surfacewhen the substrate is under load. However, rather than providingrecesses in the substrate that accommodate the sensors, preferably thesensors have a low profile that is equal to or less than 5.0 mm inthickness, even more preferably equal to or less than 3.0 mm inthickness, and suitably less than or equal to 1.0 mm in thickness.

Even more preferably, the sensors have a thickness that is equal to orless than 0.5 mm, 0.05 mm, or suitably equal to or less than to 0.01 mm.

Preferably, the area of the sensors facing the user is equal to or lessthan 400 mm², and suitably equal to or less than 100 mm², or even morepreferably less than 50 mm².

In the situation where the sensors are removably attached to thesubstrate, suitably, the sensors can be held in position on thesubstrate using either one or a combination of adhesive materialsincluding releasable adhesives or sticky adhesives, hook and loop typefasteners, clasps or any other mechanical fasteners that has a lowerprofile or does not have an adverse effect on the user by creating anincrease in pressure at a particular point.

According to an alternative embodiment, it is also possible for thesensors to be integrally incorporated in the structure of the substrate.For example, the sensors may be in the form of material located indiscrete areas or selective areas that have been physically orchemically treated so as to be able to behave as a pressure sensor.Pressure sensitive material may be in the form of foam or fibrousmaterial coated with conductive material, or pressure sensitiveconductive fibres or yarns that are either be added to a garment or forman integral part of the garment. For example, the substrate or a portionof the substrate may behave as a pressure sensor as a result of beingtreated with a conductive material in the form of a polymeric materialsuch as polypyrrole or poly(ethylenedioxythiophene) PEDOT. The substratemay be any substrate including woven fabrics, non-woven fabrics, knittedfabrics such as single or double knitted jersey, terry knits and alike.

The substrate or the portion of the substrate treated with theconductive polymeric material may include electrodes in the form of twoconductive threads, such as metal coated threads and suitably silvercoated threads that measure changes in electrical potential differencebetween the threads. Suitably, the threads are spaced apart by a spacingin the range of 2 to 15 mm and ideally approximately 5 mm in a directiontransverse to the direction in which the substrate compresses when apressure is applied to the substrate.

Suitably the substrate when treated with conductive materials behaves asa pressure sensor whereby pressure applied to the substrate isproportional to the inverse of voltage change across the sensor.

In the situation where the sensors measure are used for monitoring thebiomechanical movement of a user's foot, for example as may be usefulfor podiatry, neuropathy or orthotics investigations, analysis andtreatment, preferably, the sensors are able to be located at the heeland metatarsal region of the foot. For example, the sensors may belocated in a triangular formation at the heel of the user and located inalignment with the 1^(st), 3^(rd) and 5^(th) metatarsal of the foot.

One or more sensors may also be located in the arch of the user foot.

Although it is possible that the sensors may be located between layersof the substrate, or embedded in the substrate, preferably, the sensorsare located on an inner surface of the substrate that directly faces thesurface of the user or an outer surface of the substrate that faces awayfrom the user.

The substrate may be any form of garment depending on the particularapplication and body part being monitored such as socks, stockings,underpants, long johns, a singlet or a tubular sleeve. In the situationwhere feet of a diabetic or the stumps of an amputee are being monitoredto prevent, for example, the formation of ulcers, preferably thesubstrate is in the form of a sock or stocking. The sock or stocking maybe made from any suitable material and have any structure includingknitted, woven or non-woven structures. It is also possible that thesubstrate may be in the form of an insert, bandage, sleeve, flexibleplanar materials, pads or inner garments that covers a foot or limb of auser. One of the advantages of this embodiment is that pressure sensorscan be used to effectively measure the pressures applied by the bandagesand thus provide a valuable means to determine the pressure gradientcreated by any pressure bandaging system. Applications involvingmonitoring and controlling pressure gradients produced through pressurebandages can be used for treating venous leg ulcers or lymphoedema. Inaddition, the pressure sensors can also provide a means to determine theperformance of pressure bandaging on patients while the bandages are inuse and the effect on the patient when moving from supine to standingpositions.

According to another embodiment of the present invention, the garmentmay be in the form of a sleeve, suitably, a high stretch low pressuresleeve having pressure and temperature sensors. Once in place on apatient's limb, preferred pressure bandages can then be applied over thesleeve in a manner to produce the desired pressure gradient that isreadily displayed as the bandages are applied.

In another example the garment can be used to monitor the pressure on auser's foot. The substrate, when used for this application and in otherapplications may be in the form of an insert that covers particularsections of a foot such as the metatarsal area of a foot, the heel ofthe foot, the arch of the foot, or the upper face of the foot. Accordingto one particular embodiment, the substrate may be in the form of aninner sock that covers the foot up to the ankle and not the lower calfof the user and a conventional sock, covering the inner sock, ankle andcalf of the user may be worn over the inner sock.

Preferably, the electrical circuitry is made up of at least twoseparable parts. Preferably the circuit includes a first part of thecircuit that is disconnectable from the substrate such that it can bedisconnected and reconnected from the substrate as desired. In thesituation where the substrate is in the form of a sock, preferably thefirst part of the circuit includes valuable reusable components of theelectrical circuit including: signal conditioning or manipulation forexample to counteract noise from mains electricity, data storage, dataprocessing units, data transmission units and optionally power sourcessuch as batteries. Depending on the particular application, thebatteries may be rechargeable. Ideally, the components are contained ina housing that can be detachably connected to the substrate. Fasteningmeans such as hook and loop type fasteners, couplings, clasps and pressfasteners may be used to secure the housing in position to thesubstrate.

Preferably, the second part of the electrical circuit includes thesensors and leads that extend from the sensors to first part of thecircuit.

Preferably, first part of the circuit and housing weighs less than 300grams, suitably less than 200 grams and even more preferably less than100 grams.

Preferably the first and second parts of the circuit containco-operating pairs of contacts that electrically interconnect the firstand second parts of the circuit. For example, the leads of the secondpart of the circuit terminate in pairs of contact surfaces, hereinafterreferred to as the second contact surfaces and the housing containingthe first part of the circuit also has a co-operating pair of contactsurfaces, hereinafter referred to as the first contact surfaces.Suitably, the first contact surfaces face outwardly from the back orunderside of the housing that is positioned against the substrate. Inthe situation where the substrate is in the form of a sock, preferablythe second contact surfaces are located at the upper section or adjacentto the opening of the sock.

The leads may be in the form of conductive fibres, yarns or threads orribbon and bus connections that are supported by the substrate. Althoughit is possible that the leads may be incorporated in the substratepreferably, the leads are sewn, knitted or woven to the substrate sothat the substrate can flex and/or stretch in substantially the samemanner as if the conductive yarns were absent. For instance leads in theform of ribbon and bus connections may flex and stretch in an elastic orresiliently deformable manner.

Alternatively, in the situation in which the leads such as ribbon andbus connectors are not elastic or resiliently deformable, it is possiblethat the leads may be supported on the substrate so as to move between acorrugated or tortuous condition, while the substrate is not flexed orstretched, to an at least partially or fully straightened condition,when the substrate is flexed or stretched.

Preferably, the system and garment of the present invention may alsoinclude any one or a combination of sensors for monitoring or sensingtemperature of the user, stress and strain of parts of the user,angulation of particular parts of the user or sensors for monitoringphysiological conditions such as the make up of the sweat or exudate ofthe user.

The temperature sensor may be any suitable thermocouple. Similarly, thebiomechanical angulation sensor and the stress and strain sensors may beany suitable sensor including a conductive polymeric material orresistive change sensors that change in electrical resistance as aresult of changes in angulation of parts of the body or forces such asthe forces in posterior and anterior sections of a ankle or knee joint.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described withreference to the accompanying drawings, of which:

FIG. 1 is a perspective view of a sock having a detachable housingcontaining re-useable components of an electrical circuit that is fittedto the sock;

FIG. 2 is an underneath view of a pair socks that are substantially thesame as the sock shown in FIG. 1, each sock having a set of sensors thatare located on the sock so that, when the sock is worn, the sensorsalign with the metatarsal and heel of the foot;

FIG. 3 is an enlarged cross-sectional view of one of the sensors of thesock shown in FIG. 1 or 2;

FIG. 4 is a perspective view of the sock shown FIG. 1 without thedetachable housing fitted to the sock;

FIG. 5 is a back view of the detachable housing shown in FIG. 1;

FIG. 6 is a photograph of a sock substantially the same as that shown inFIGS. 1 to 5;

FIG. 7 is a graph illustrating a set of results obtained using the sockshown in FIG. 6;

FIG. 8 is a graph illustrating the changes in voltage measured across awool polypyrrole pressure sensor;

FIG. 9 is a chart showing the compression properties of a range offabrics measured using a Hounsfield Jaw;

FIG. 10 is a graph illustrating the relationship between the pressuremeasurements and an inverse of voltage squared of a fabric sampletreated with PEDOT;

FIG. 11 is a graph illustrating changes in voltage across a sensor inthe form of a wool fabric treated with PEDOT located on the ball of afoot of a wearer during a trial;

FIG. 12 is a graph illustrating an enlarged view of the graph of FIG. 11over the time interval between 45 and 60 seconds;

FIG. 13 is a graph illustrating changes in voltage across a sensor inthe form of wool fabric treated with PEDOT located on the heel of a footof wearer during a trial;

FIG. 14 is a graph illustrating an enlarged view of the graph of FIG. 13over the time interval between 40 and 60 seconds;

FIG. 15 schematically illustrates a series of steps for manufacturing afabric sensor treated with PEDOT;

FIG. 16 schematically illustrates the sole of a foot and toes as iffitted with a series of pressure sensors; and

FIG. 17 is a bar graph illustrating a set of signals of the sensorsshown in FIG. 16 during a trial.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will now be described in detailwith reference to a sock 10 shown in the Figures. However, it will beappreciated that the present invention may be embodied in any type ofgarment including, but by no means limited to stockings, leggings,underpants, long johns, singlets, inserts, inner socks, inner garments,under garments or bandages and may also be applicable in situationswhere the garment is used to cover the stump or terminated limb of theamputee that is fitted into a prosthetic limb.

The sock 10 according to the preferred embodiment has been specificallyconfigured to be a comprehensive analytical and monitoring tool forpatients having neuropathic or orthotic conditions. The sock has beendevised with sensors that monitor biomedical movement and in particularmeasure force or pressure at desired positions on the load bearingsurface, temperature of the patient's foot and optionally, stress orstrain of the foot. Although it is beyond the scope of the presentinvention, the data obtained from the sensors can be analysed by aqualified health care practitioner.

The sock shown in FIG. 1 comprises conductive yarns 11 such as silvercoated yarns sewn to the outside face of the sock, sensors 12 located atthe base of the sock 10 that may align with the heel and metatarsalregions of a foot wearing the sock 10, and a detachable housing 13containing the electrical circuitry located on the upper end of the sock10. Although it is possible that the yarns 11 may be elasticised whichwill allow the sock 10 to stretch and flex, in the situation where theyarns 11 are not elasticised, preferably the yarns 11 are sewn to thesock in a manner that allows stretching, for example, in a zig-zag ors-shaped pattern that allows the sock 10 to stretch and flex in theusual manner. The yarns 11 extend from the upper band of the sock 10where the yarns 11 are arranged in pairs of terminating points 14 to thesensors 12 located on the base of the sock 10. As can be best be seen inthe FIG. 3, the yarns 11 are sewn, knitted or otherwise incorporatedinto the sock 10 save for a length 15 of the yarn closest to the sensors12 that is free from the base of the sock 10. In essence, the freelength 15 of the conductive yarn allows the sensors 12 to be moved andpositioned on the sock 10 at desired locations. The sensors 12 may befixed in position using releasable adhesive, micro hook and loop typefasteners or an overlapping cover such as an adhesive tape that retainsthe sensors 12 in the desired position.

As can be seen in FIGS. 2 and 16, preferably three pressure sensors 12a, 12 b and 12 c are located in the triangular formation at the heel ofthe sock 10 and, in addition, three separate sensors 12 d, 12 e and 12 fare located on the sock 10 that align with the first, third and fifthmetatarsal of a patient wearing the sock 10.

In our view an important characteristic of the sensors 12 that they havea low or thin profile, preferably in approximately 0.5 mm or less andhave surface area in the range of 50 to 100 mm². One example of apressure sensor 12 is a thin film sensors sold under the trade nameFLEXIFORCE® by Tekscan, Inc. An advantage in the using a thin filmsensor 12 is that the presence of the sensor 12 on the sock 10 does notcause an increase in pressure in the foot, stump or any other loadingbearing surface that could cause an adverse physical effect to a medicalcondition such as neuropathy.

Although not shown in the Figures, temperature sensors or sensors formeasuring any other physical or physiological condition may also befitted to the sock. Examples of suitable temperature sensors aresemi-conductor type sensors or RTD type sensors or yarn and/or fabrictype sensors.

The conductive yarns 11 extend from the sensors 12 at the base of thesock 10 to an upper edge of the sock 10 where the yarns end in pairs ofterminating points 14. The terminating points 14 are arrangedside-by-side and align with co-operating pairs of contact points 16located on the underneath side of the detachable housing 13. Althoughnot shown in the Figures, an electrical conductive adhesive sold underthe trade name ARclad™ 8001 by Adhesive Research, Inc. Glen Rock, Pa.17327 is applied to either one or both of the terminating points or thecontact points of the detachable housing 13. In addition to electricalcoupling, the detachable housing 13 is also secured to the upper portionof the sock 10 using any conventional securing means such as buttons,straps and buckles, co-operating hook and loop type fasteners and, asillustrated in the FIGS. 4 and 5 press studs 17.

In order to allow the sock 10 to be worn by elderly, frail and patientswith impaired or compromised bodily movement, preferably the detachablehousing 13 is light weight and suitably less than 200 grams in weight.If necessary, the top band of the sock 10 can be reinforced withadditional elastic to prevent movement of the sock 10 and housing duringwalking. Other means such as releasable adhesive or sticky adhesive mayalso be employed to ensure that the top band of the sock stays in acomfortable and working position. The detachable housing 13 containselectrical circuitry suitable for supply power to the sensors andreceiving signals from the sensors. For example, the housing 13 containsa rechargeable battery, a processing unit that can be programmed withsuitable algorithms able to be customised for particular applications,data storage and if desired, a transmitter that wirelessly sends signalsto a host device or computer that the can further process data of thesensors worn by one patient or multiple patients wearing the socksimultaneously. The circuitry contained in the housing 13 may be madeusing any standard hardwiring.

Although it is ultimately dependant on the condition that is beingmonitored, in the situation where the sensors are monitoring pressure wehave found that a primary data sampling rate of the sensors in the rangeof 500 to 1,500 Hz and suitably approximately 1,000 Hz to provide ampledata. The optimal rate at which data from the sensors is sampled isdependant on a number of factors including:

-   -   the size of the power source available; and    -   the nature of the data required to provide meaningful feedback        to the health care practitioner.

In addition, the processing unit may carry out data modification ormanipulation, for example, noise reduction, to moderate the amount ofthe data required to be stored. In any event, ideally the available datamemory and power supply are capable of the continuous operation for aperiod of at least one day. The status of the patient's condition canchange over the course of a day and, therefore, the device should beable to operate for a period of at least one day.

The sock will have immediate application in the podiatry and orthopaedicfields to provide extensive data regarding walking behaviour with andwithout footwear and on all surfaces. The sock may also be applied tospecialised limb socks in the prosthetic field. This data could be usedto diagnose the onset of problems related to particular parts of thefoot or limb.

In neuropathic conditions, where there is a decline in the efficiency ofthe venous system due to disease, the indication from temperature andpressure sensors may be effective in diagnosing problems. A change inwalking behaviour, as a person becomes less conscious about footmovement, due to fatigue, or a decline in nervous response as aconsequence of their neuropathy, or certain risk walking patterns, iseither not detectable or not easily detectable by present devices. Therealso may be footwear related issues that are not apparent from currentmeasuring systems.

Long term, time based, measuring of actual pressure at key indicatingpoints of a foot combined with temperature measurements and othermeasurements like strain could provide a strong indication of adegenerating condition that could result in a pressure ulcer. Inaddition to the diagnostic function of the sock there is provided amonitoring function via a means to wirelessly transmit the data to localor remote systems. This could provide warnings to the wearer or to careproviders about at risk conditions.

FIG. 7 is a graph illustrating a set of data obtained using the sockshown in FIG. 6. The graph illustrates data obtained from pressuressensors located at the heel, fifth metatarsal, third metatarsal, firstmetatarsal and big toe. The date shown in the graph was obtained by thepatient walking from a hard concrete floor to a soft carpeted surface.The different sensor responses provide a clear indication of the walkingbehaviour and characteristics.

In addition, the sock could also provide a means to analyse athleticbehaviour for running, walking and jumping in time based pressure,temperature and strain measurements. For example running patterns understress may provide an insight into endurance levels, the onset ofphysical problems or a means to correct or improve running action. Thistype of analysis may assist in developing corrective solutions. The datamay also provide an analysis of the physical capability of athletes asit could indicate a change in running or walking patterns as the limitsof endurance are reached. This could provide valuable information forcoaches.

In another example, rather that using the thin film sensor describedabove it is possible for the sensor to be a substrate having surfacesthat are treated with a conductive polymer such as polypyrrole orpoly(ethylenedioxythiophene) (PEDOT) and has variable conduction orresistance depending on the force applied to the substrate.

Those skilled in the art will appreciate that many modifications andvariations may be made to the preferred embodiment described abovewithout departing from the spirit and scope of the present invention.

The sock 10 may be any conventional sock 10 that has been retro-fittedwith the required elements according to the present invention oralternatively a specialised sock that has been purposely built.Moreover, the sensors may be fitted or removably connected to asubstrate in any form including bandages, inserts that are worn under orover a conventional item of clothing such as socks, stockings,underpants and alike. For example, in the situation where the sensorsare monitoring pressure on a wearer's feet, the substrate may be in theform of a mini sock or ankle sock that only comes up to the ankle of thewearer and a conventional sock is then fitted over the mini or anklesock.

According to another embodiment, any one or a number of sensors formonitoring physical conditions such as temperature, stress, strain orangulation and/or sensors for monitoring physiological conditions suchas the make up or properties of sweat and body exudate may be included.

According to yet another embodiment, it is possible that the part of theelectronic circuitry contained in the housing 13 may be in the form ofprinted electronic circuitry. The printed circuitry may be containedwholly or partly within the housing or partly or wholly on thesubstrate.

FURTHER EXAMPLES

As described above, the present invention may be embodied in any type ofgarment including, but by no means limited to stockings, leggings,underpants, long johns, singlets, inserts, inner socks, inner garments,under garments or bandages and may also be applicable in situationswhere the garment is used to cover the stump or terminated limb of theamputee that is fitted into a prosthetic limb. In addition to theanalysis of foot or limb related activity, the garment may also be usedin a broad range of analysis or monitoring of medical conditions.

An effective and widely used means for treating venous leg ulcers andvarious wounds is application of pressure bandages. As an example legulcers are a chronic condition caused by a range of clinical disorders,either individually or in combination but to a large extent areassociated with underlying venous/arterial disease. The incidence ofulceration in the population increases with ageing. Diabetes is acondition that is a significant cause of ulceration.

Another condition where use of pressure garments or bandages are usefulis Lymphoedema, a chronic swelling of the limbs due either to a poorlymphatic system that fails to adequately drain fluids or can be theresult of surgery or radiotherapy. There is a high potential fordevelopment of leg ulcers known as lymphatic obstruction oedema.

The use of compression bandages is now generally accepted as aneffective means to minimise or reverse the negative vascular changes byforcing fluid from the interstitial spaces back into the vascular andlymphatic systems. Generally though, the correctly applied pressure willbe reduced progressively up the limb or leg and it is usual thatexternal compression bandages are applied in a graduated fashion, withthe highest pressure at the ankle.

However the actual pressure required remains a matter of some debate asthere is not currently a means to effectively measure and monitor thepressure at the skin once bandages have been applied and patients leavea clinician. Pressures ranging from 15 to 50 mm of Hg have beendescribed although there is debate on what is appropriate for variouspatients and their conditions. Pressures of about 40 mmHg at the ankleare widely quoted in the literature for the prevention or treatment ofvenous leg ulcers, but some authorities recommend values significantlyhigher than this.

The pressure exerted by any pressure bandage is determined by theelasticity of the fabric, the physical shape of the limb, the number offabric layers applied to the limb and the manner of application.

There are many bandage systems, comprising 1 or more layers, availablefor providing a pressure gradient. A bandage correctly applied withconstant tension to a limb of normal proportions will automaticallyproduce graduated compression with the highest pressure at the ankle.This pressure will gradually reduce up the leg as the circumferenceincreases. However there is no uniformity in limb shapes and dimensionsso that there are great variations for patients that can only becontrolled by the expert experience of the clinician applying thebandages. Too little pressure or an inadequate gradient will beineffective in the healing process, too high a pressure can result inlocalised pressure points that could lead to complications.

There is little actual pressure data to determine the effects ofpressure on the wide population affected by such conditions and evenless data available on the effect when an individual moves from a supineto a standing position or sits for extended time. For example if bloodcollects in the vessels and sinuses of the lower leg, under theinfluence of gravity, causes the volume of the leg to increase and isassociated with the formation of oedema, leg volume will increase andlead to pressure changes.

It is dependant on clinicians who are expert in the choice of productsfor particular patients and the optimum means for applying anyparticular product to avoid these complications.

The present invention may be used in a broad range of applicationsincluding bandages or pressure bandages in the sense described above.One of the advantages provided by this particular embodiment of thepresent invention is that effective measurement of the pressures appliedby pressure bandages and a valuable means to determine the pressuregradient created by any pressure bandaging system. In addition it canalso provide a means to determine the performance of pressure bandagingon patients while the bandages are in use and the effect on the patientwhen moving from supine to standing positions.

According to another embodiment of the present invention, the garmentmay be in the form of a high stretch low pressure producing fabricsleeve that can be readily applied to a patient. The sleeve has a numberof pressure and temperature sensors and conducting circuits from eachsensor to a common termination point at one end of the sleeve. As withthe sock the sensors/sleeve is able to be readily connected, ordisconnected from, to a removable electronics band or small device thatprovides power for the sensors and is able to then transmit the sensordata to a remote device for data analysis or simple display. In anotherform the pressure and temperature sensors are contained in a wrap aroundfabric to be used as a first layer prior to application of the pressureproducing bandages.

Once in place on a patient's limb preferred pressure bandages areapplied in a manner to produce the desired pressure gradient that isreadily displayed as the bandages are applied.

It should be appreciated that this approach is not limited to fabrics orsleeves directed at limbs but can be applied to other garments. Forexample the sensors could be incorporated into undergarments for use byparaplegics or quadriplegics to sense the contact with seat or othersurfaces to determine and alert whether there are risks for developingpressure points that could lead to complications.

The pressure sensors used in the present invention may be in a number ofdifferent forms. For example, pressure sensors from Tekscan are one formof sensor that can be used. An alternative sensor is the type of sensorin which a substrate, such as a substrate made from wool fibre, istreated with conductive polymers such as polypyrrole orpoly(ethylenedioxythiophene) (PEDOT).

Techniques for applying conductive polymers to flexible substratesinclude, but are by no means limited to the following known techniques:roll to roll coating, inkjet printing dispersions and physical vapourdeposition. Furthermore, examples of two journal articles that describetechniques for applying conductive polymers to a base fabric substratesuitable for use as a pressure sensor are as follows.

1. ADVANCES AND APPLICATIONS OF INHERENTLY CONDUCTIVE POLYMERTECHNOLOGIES BASED ON POLY (3,4-ETHYLENEDIOXYTHIOPHENE) by Simpson etal, 2005 AIMCAL Fall Technical Conference and 19^(th) InternationalVacuum Web Coating Conference, Oct. 16-20, 2005

2. APPLICATION OF POLYPYRROLE TO FLEXIBLE SUBSTRATES by Winter-Jensen,Clark et al.

The performance of fabric samples treated with a polypyrrole and PEDOTwill now be described in further detail.

FIG. 8 illustrates the test results of a wool fabric sensor treated witha polypyrrole conductive polymer. The test was carried out using aLabjack data collector to detect relative responses between gentle taps,thumb pressure and sharp taps applied to the fabric. As can be seen, theconductivity of the material increases and thus the potential differencereduces with pressure applied to the fabric.

The pressure sensing performance of a fabric treated with a conductivepolymer is to an extent dependant on the compressibility performance ofa fabric. The compression of fabric can be measure in two forms, namelya static test in which a weight is placed on the fabric and a dynamictest whereby a weight is dropped onto the fabric.

A variety of fabric types were trialed to determine the relativecompression characteristics, with the thought that the more compressiblefabrics would have a better range as conductive pressure sensors. AHounsfield test equipment apparatus HS000M was used to exert acontrolled pressure (maximum applied weight=50 Kg or 530N) onto thechosen fabric pieces and the compression noted. A calibration graph wasfirst prepared for jaw separation distance, to enable the relativefabric compressions to be calculated from the resultant mV readingsobtained at maximum possible compressions. Once the device wascalibrated the compression characteristics for a set of differentfabrics was measured. The compression characteristics of a set offabrics tested is set out in FIG. 9. Fabrics having poor totalcompression were determined to be unsuitable for treatment with aconductive polymer. Absolute compression heights of at least 1.0 mmwhere determined to be the most suitable.

A PEDOT wool sensor was constructed in accordance with the sequence ofsteps set out in FIG. 15 and then tested. The step 1 involves applying aconductive polymer a section of sock fabric identified by referencenumeral 20 in accordance with techniques such as those discussed in theabove journal articles. Conductive threads in the form of silver coatedthreads 21 are spaced approximately 5 mm apart are then sewn into theconductive polymer section and non-conductive thread 22 is sewn aroundthe outside of the conductive material. A lightweight greaseproof paper23 is then folded over the sensor to form a paper envelope over thesensor. A waterproof medical gown fabric 24 is then wrapped around thesensor. Finally excess material is cut away from the sensor.

Static tests were then conducted on the sensor shown in FIG. 15 over arange of different pressures using a Hounsfield Jaw apparatus. Theresults obtained show a relationship between the pressure applied and1/V² which is illustrated by the graph in FIG. 10.

Two identical sensors constructed in accordance with FIG. 16 were thenlocated in the ball and heel of a wearer in the weight range of 65 to 70kg and then asked to perform a series of separate movements. FIG. 11illustrates the results obtained of a sensor located at the ball of thewearer's foot when requested to carry out activities. Specifically, theinitial dips between 10 and 15 seconds indicate the wearer transferringall of their weight between standing on two feet and standing on onefoot fitted with the sensor. The interval between 30 and 40 secondsrepresent a wearer taking the weight off their heels and the intervalfrom 40 to 60 seconds represents a wearer marching while the intervalfrom 63 second to 70 seconds presents the wear hopping. FIG. 12 is anenlarged view of FIG. 11 over the interval 45 to 60 seconds.

FIG. 13 illustrates the response obtained from a sensor located at theheel of the wearer while the wearer performs a series of differentmovements. In particular, during the interval 15 to 25 seconds, thewearer transfers their weight from a position in which their weight isevenly distributed on their feet to a position in which their weight isunevenly distributed to the heel followed by a rocking motion forwardand then finally back again onto the back of the heel. The interval from28 to 35 seconds represents the wearer rocking from side to side. Theinterval from 40 to 50 seconds represents the response from the marchingand the interval from 55 to 60 seconds represents the response obtainedduring hopping on two feet.

FIG. 14 is an enlarge view of the response during marching and hoppingactivities during the interval from 40 to 55 seconds.

A trial was then run in which both PEDOT fabric sensors and TekscanFlexiforce sensors were operated simultaneously. The trial involved 3single PEDOT jersey sensors placed on the inner and outside heelpositions, namely positions H1 and H2 in FIG. 16 and a double interlockknit PEDOT sensor placed in the middle heel position H3. Tekscan sensorswere placed on the remaining foot pad and big toe position, identifiedin FIG. 16 as M1, M2, M3 and BT. The trial was carried out by the sockbeing worn around the laboratory, for a period of 1.5 hours.

FIG. 17 is a graph showing an instantaneous output for the sensors inorder of Left to Right: H3, H2, H1, M3, M2, M1 and BT.

At the end of the trial all sensors were tested using the Hounsfield Jawapparatus and all were measured as having pressure responses as afunction which caused an inverse voltage change. Thus, all sensors wereshown to be responsive and still in working order after the trial.

The claims defining the invention are as follows:
 1. A system that iswearable by a person to monitor or sense pressure, the system including:a) a flexible substrate in the form of a garment that can be worn by orfitted directly or indirectly to surfaces of the person subject to loadsor pressure; and b) at least one pressure sensor fixed to the substrateor movably connected to the substrate, with leads extending, from eachpressure sensor, the leads terminating, in contact surfaces located onan external surface of the flexible substrate and spaced a distance froman edge boundary of the flexible substrate.
 2. The system according toclaim 1, wherein the at least one pressure sensor has a low profile thatis equal to or less than 5.0 mm in thickness.
 3. The system according toclaim 2, wherein the at least one pressure sensor has a low profile thatis equal to or less than 0.5 mm in thickness.
 4. The system according toclaim 1, wherein the at least one pressure sensor is held in position onthe substrate using either one or a combination of adhesive materials,hook and loop type fasteners, clasps or other mechanical fasteners thathave a low profile.
 5. The system according to claim 1, wherein the atleast one pressure sensor comprises a material selected from the groupconsisting of: conductive yarns or threads and metal coated threads oryarns, and wherein the at least one sensor comprises substantially inertelectrodes to measure a change in electrical potential difference acrossthe sensor.
 6. The system according to claim 1, wherein the at least onepressure sensor comprises a material selected from the group consistingof: conductive yarns or threads and conductive polymers that are spacedapart by a spacing in the range of 2 to 15 mm in a direction transverseto the direction in which the substrate compresses.
 7. The systemaccording to claim 1, wherein the at least one pressure sensor has anarea substantially transverse to a direction of pressure applicationthat is equal to or less than 400 mm².
 8. The system according to claim1, wherein the at least one pressure sensor is used for monitoringbiomechanical movement of the person's foot and the at least onepressure sensor is located at a heel, metatarsal or arch region of theperson's foot.
 9. The system according to claim 1, wherein the substrateis a garment in the form of one of socks, stockings, underpants, longjohns, a singlet, leggings, inserts, inner socks, inner garments, undergarments, tubular sleeves, or garments used to cover a stump orterminated limb of an amputee.
 10. The system according to claim 1,wherein the at least one pressure sensor can be used to monitor thelevel of pressure applied to the person by an external source, and theflexible substrate is in the form of a compression garment.
 11. Thesystem according to claim 1, additionally comprising electricalcircuitry that receives signals from the contact surfaces located on thesubstrate that communicates with the at least one pressure sensor,wherein the electrical circuitry is provided in a first housing that isconnectable to and disconnectable from the contact surfaces located onthe substrate as desired.
 12. The system according to claim 11, whereinthe circuitry provided in the first housing includes reusable componentsof an electrical circuit including: signal conditioning components; datastorage; data processing units; and data transmission units.
 13. Agarment that is wearable by a user to monitor or sense pressure eitherseparately or in combination with any one or more of temperature,stress, strain, angulation or as physiological condition, the systemincluding; a) a flexible substrate: that can be worn by, or fitteddirectly or indirectly to surfaces of a user subject to pressure orforces; and b) at least one discrete pressure sensor that is fixed tothe substrate or movably connected to the substrate having conductiveleads that are sewn, knitted or woven to the substrate and terminate incontact surfaces located on an external surface of the substrate andspaced a distance from an edge boundary of the substrate, wherein thesubstrate and sensors can be worn directly or indirectly againstsurfaces of the user and the sensors can be positioned at desiredlocations without causing an increase in pressure on load bearingsurfaces as result of the presence of the pressure sensors.
 14. A methodof monitoring or treating a subject, the method including the steps of:placing a garment comprising a flexible substrate having one or morediscrete pressure sensor(s) with conductive leads terminating in contactsurfaces located on an external surface of the substrate and spaced adistance from an edge boundary of the substrate in contact with thebuttock, hand, or limb of the subject; mounting circuitry containingcooperating contacts that electrically connect to the contact surfaceslocated on the garment to position the circuitry on the garmentsubstrate; and monitoring the pressure readings attributable to eitherthe weight of the patient or the pressure applied externally to thesubject.
 15. The method according to claim 14, comprising placing apressure sensitive garment in contact with the foot of the subject,wherein the at least one discrete pressure sensor is located on a partof the subject's foot including a ball, heel or toe of the subject'sfoot.
 16. The method according to claim 14, additionally comprisingpositioning contact surfaces of a detachable housing in contact with thecontact surfaces located on the external surface of the garment, whereinthe detachable housing additionally comprises data storage and datatransmission capability.
 17. The garment of claim 13, wherein the atleast one discrete pressure sensor is in the form of material located inat least one discrete area of the garment.
 18. The garment claim 13,wherein the substrate comprises a woven fabric, a non-woven fabric, or aknitted fabric.
 19. The garment of claim 13, wherein the substrate is inthe form of a sock comprising a knitted, woven or non-woven substrate.20. The garment of claim 19, wherein the sock covers the foot up to theankle and not the lower calf of the user.
 21. The garment of claim 20,wherein the contact surfaces are adjacent an opening of the sock. 22.The garment of claim 13, wherein the leads are sewn, knitted or woven tothe substrate, whereby the substrate can flex and/or stretch insubstantially the same manner as if the leads were absent.
 23. Thegarment of claim 13, additionally comprising a temperature sensor.
 24. Amethod for long term, time-based monitoring of pressure exerted by oragainst a body area of a user, comprising: placing a garment comprisingat least one discrete pressure sensor with conductive leads terminatingin contact surfaces located on an external surface of and spaced adistance from an edge boundary of the garment in contact with thebuttock, hand, foot or limb of the user; positioning contact surfaces ofa detachable housing in contact with the contact surfaces located on thegarment, wherein the detachable housing additionally comprises datastorage and data transmission capability; and monitoring pressurereadings attributable to either the weight of the user or pressureapplied externally to the user at locations corresponding to the one ormore discrete pressure sensor(s).
 25. The method of claim 24, whereinthe garment is a sock and the contact surfaces are positioned adjacentan opening of the sock.
 26. The method of claim 24, wherein the garmentis selected from the group consisting of stockings, leggings,underpants, long johns, singlets, inserts, inner socks, inner garments,undergarments, and garments used to cover a stump or terminated limb ofan amputee.
 27. The system according to claim 1, wherein the leadscomprise conductive fibers, yarns, threads or ribbon that are sewn,knitted or woven into the substrate.
 28. The system according to claim27, wherein the leads are elastic or resiliently deformable.
 29. Thesystem according to claim 1, wherein the leads are supported on thesubstrate so as to move between a corrugated or tortuous condition whenthe substrate is not flexed or stretched and an at least partiallystraightened condition when the substrate is flexed or stretched. 30.The system according to claim 1, wherein the contact surfaces align withcooperating contact points located on a detachable housing.
 31. Thesystem according to claim 30, wherein the detachable housing containselectrical circuitry for supplying power to and receiving signals fromthe at least one pressure sensor.
 32. The system according to claim 30,wherein the detachable housing curtains a rechargeable battery.
 33. Thesystem according to claim 30, wherein the detachable housing contains aprocessing unit programmed with algorithms.
 34. The system according toclaim 30, wherein the detachable housing contains a transmitter thatwirelessly sends signals to a host device or computer.
 35. The systemaccording to claim 30, wherein the flexible substrate is in the form ofa sock and the detachable lousing is mountable to an upper portion ofthe sock.
 36. The system according to claim 1, additionally comprisingat least one additional sensor capable of monitoring at least one of:temperature, stress, strain, angulation and a physiological condition ofthe person.
 37. The system according to claim 1, wherein the at leastone pressure sensor comprises a surface treated with a material having avariable resistance depending on the force applied to the substrate. 38.The system according to claim 37, wherein the material is a polymericmaterial comprising polypyrrole or poly(ethylenedioxythiophene).
 39. Thesystem according to claim 1, wherein the at least one pressure sensorcomprises a thin film sensor.